Liquid toner imaging (printing and copying) systems that utilize intermediate transfer members are well known. Representative systems are described in U.S. Pat. Nos. 4,984,025; 5,028,964; 5,555,185; 5,410,392; 5,636,349; and many other patents and patent applications assigned to the assignee of the present application, the disclosures of which are incorporated herein, by reference. Such systems contain an intermediate transfer member (ITM) that receives a liquid toner image from one surface (for example, a surface on which the image is formed) and from which the image is transferred (for example, to a final substrate).
In general, transfer to ITMs is by electrical attraction of the charged toner particles from the image forming surface. This, first, transfer may be aided by heat. In many systems first transfer requires conformance between the surface of the ITM and the image forming surface, under low pressure. In many systems, the image is heated on the ITM so that it coalesces. The image is generally transferred to the final substrate by heat and pressure (hereinafter “second transfer”).
In order to perform its tasks, the ITM is generally required to meet a number of physical requirements. These include release requirements of the surface of the ITM (hereinafter the “release surface” or “release layer”) for release of the image from the intermediate transfer member to the final substrate (or to a second ITM). Suitable release layers are described in the above referenced references and generally include a silicone layer of specified construction.
However, one of the major limitations of such release layers is a gradual loss of release properties which results in incomplete transfer of the image to the final substrate. Such incomplete transfer, in addition to causing a reduction in quality of the image, also requires that the ITM be cleaned after each second transfer cycle, a process that greatly complicates the system. Furthermore, such continuous cleaning further reduces the life of the transfer surface.
Representative intermediate transfer members are described in the above referenced patents and applications and in U.S. Pat. Nos. 5,754,931; 5,592,269 and 5,745,829 and published applications WO 97/07433; WO 98/55901 and WO 00/31593, the disclosures of all of which are incorporated herein by reference.
Representative systems that incorporate the technology described in at least some of these and many other patents and patent applications include EBONY, E-PRINT PRO+; TURBOSTREAM, ULTRASTEAM 200 and 400 and PUBLISHER 2000 and 4000, OMNIUS WEBSTREAM, WEBSTREAM 100, WEBSTREAM 200, WEBSTREAM 400 and OMNIUS MULTISTREAM produced and marketed by Indigo NV, a subsidiary of The Hewlett-Packard Company, the assignee of this application.
PCT Publication WO 96/13760 (now U.S. patent application Ser. No. 08/809,419), the disclosure of which is incorporated herein by reference, describes a liquid toner in which a two component carrier liquid is used. The carrier liquids are adsorbed or solvated by the release surface. The major component of the carrier liquid has a relatively higher volatility that the minor component of the carrier liquid. During operation, the less volatile component remains adsorbed in the release layer to reduce inter alia the drying out of the layer. This improves the release of the layer and the gloss of the resultant image. It also results in some increased release layer life.
U.S. Pat. No. 5,300,390, the disclosure of which is incorporated herein by reference describes a liquid toner with improved cohesivity. This increased cohesivity improves the transfer efficiency of the image. In particular, this patent describes the use of non-soluble ground silicone gels or silicone oils. The silicone gels are present in an amount of between 1-30% by weight of gel to toner particles and the silicone oil in an amount of 5% by weight with respect to the toner particles.